Power circuit breakers of the generic type are known. By arranging them in their withdrawable-part rack, they can be inserted or withdrawn in or from a switchgear assembly in a simple manner. In this case, significant importance is given to locking the power circuit breaker in its withdrawable-part rack.
In particular in the case of power circuit breakers having a high short-circuit disconnection capacity, a force occurs, owing to the loop effect of the current path of the power circuit breaker or of the switchgear assembly, which acts on the power circuit breaker. This force is directed such that the power circuit breaker is forced out of its withdrawable-part rack.
In particular in the case of high flowing currents (short-circuit currents), considerable forces acting on the power circuit breaker occur since the force acting rises with the square of the current. If in this case the power circuit breaker is not fixed in its withdrawable-part rack precisely in the line of action of this force, the power circuit breaker may be subjected to a torque owing to leverage. The result is that the power circuit breaker experiences a tipping movement which leads to a relative movement between the connection pieces of the switching contacts of the power circuit breaker and the contact laminations of the withdrawable-part rack.
This relative movement may lead to a separation of the switching contacts from the contact laminations, with the result that arc formation cannot be ruled out. As a result of the high flowing currents, destruction of the power circuit breaker would be associated with this.
It is known to latch the power circuit breaker with its withdrawable-part rack by way of a latching device. In this case, retaining systems are known which are actuated by an insertion shaft or an insertion drive for the purpose of inserting the power circuit breaker in the withdrawable-part rack. Such retaining systems, however, are typically of a complex design. Furthermore, a minimum amount of play is provided between the restraining elements of the retaining system and the withdrawable-part rack, since only a simultaneous movement between the power circuit breaker and the withdrawable-part rack and lifting-out of the restraining systems is possible.
In addition, rigid systems are known, by which the insertion direction or the withdrawal direction of the power circuit breaker in or out of the withdrawable-part rack can be blocked. These systems have a relatively small, effective lever arm, such that the high forces which occur in particular in the case of a short-circuit cannot reliably be absorbed.
DE 196 47 747 C1 discloses an insertable device carrier having a latching device. In this case, a latching rod is displaced at the same time owing to a rotation of an actuating shaft of a main breaker. The latching rod in turn displaces a blocking slide. The result is that latching of the device carrier takes place.
As a result, single-point latching of the device carrier is achieved such that it is positioned. However, if high forces are acting owing to high currents flowing (short-circuit currents), the latching rod known from DE 196 47 747 C1 forms a lever arm such that a displacement of the device carrier. Accordingly, a power circuit breaker from the desired latched position cannot be ruled out. The point of engagement of the latching rod in a latching opening in a device floor in this case acts as a pivot in order that a deflection of the latching rod can take place.